The World Health Organization has announced that Zika virus infection, a mosquito-borne illness that in the past year has swept quickly throughout equatorial countries, is expected to spread across the Americas and into the U.S.
The symptoms of the disease include a rash, headache, and mild fever. However, a May 2015 outbreak in Brazil led to nearly 3,500 reports of microcephalic infants linked to the virus, even after its symptoms had passed, and an uptick in cases of Guillain–Barre syndrome, an immune disorder. In the U.S., the Centers for Disease Control and Prevention (CDC) has issued a travel alert advising pregnant women to avoid traveling to countries where the disease has been recorded.
Zika virus is transmitted by the mosquito species Aedes aegypti, also a carrier of dengue fever and chikungunya, two other tropical diseases. Although Aedes aegypti is not native to North America, researchers at the University of Notre Dame who study the species have reported the discovery of a population of the mosquitos in a Washington, D.C., neighborhood. The team found genetic evidence that these mosquitoes have overwintered for at least the past four years, meaning they are adapting for persistence in a northern climate well out of their normal range.
While the Washington mosquito population is currently virus-free, team leader Dr. David Severson of the Notre Dame Department of Biological Sciences noted that the ability of this species to survive in a northern climate is troublesome. The mosquito is typically restricted to tropical and subtropical regions of the world and is not found farther north in the U.S. than Alabama, Mississippi, Georgia, and South Carolina.
“What this means for the scientific world,” Severson said, “is some mosquito species are finding ways to survive in normally restrictive environments by taking advantage of underground refugia. Therefore, a real potential exists for active transmission of mosquito-borne tropical diseases in popular places like the National Mall. Hopefully, politicians will take notice of events like this in their own backyard and work to increase funding levels on mosquitoes and mosquito-borne diseases.”
The team published their findings in the American Journal of Tropical Medicine and Hygiene.